The use of insect repellents is widely accepted throughout the world. Besides repellents intended for outdoor use, repellents are also available for use in homes to repel pests such as cockroaches, termites, ants, fleas, and so forth. The commercial standard for insect repellency is N,N-diethyl-3-methylbenzamide (DEET). The U.S. Environmental Protection Agency (EPA) estimates that more than 38% of the U.S. population uses a DEET-based insect repellent every year and that worldwide use exceeds 200,000,000 people annually (U.S. Environmental Protection Agency, PBS1-207722, 1980). However, DEET is known to cause severe adverse health effects in some people, particularly in higher concentrations. (See, for example, Qui et. al., 1998, J. Am. Mosq. Control Assoc. 14 (1):12-27; Miller, J. D., 1982, New Eng. J. Med. 307:1341-1342; Roland, et. al., 1985, Can. J. Med. Assn. J. 132:155-156).
Over the last several years effort has been directed toward the development of natural repellents. Much of this initiative is due not only to the toxic effects of traditional repellents, but to increased government regulation of certain chemicals in insect pest management (e.g., DEET, naphthalene, dimethyl phthalate, etc.) and the desire to use products which are more environmentally friendly than traditional chemicals.
Naturally derived biorepellents have been investigated as a group of chemicals that have biological activity and can cause repellent or insecticidal effects without negative impacts on human safety or the environment. Many plant oils and extracts have been identified as insect deterrents, repellents or toxins. These include botanical insect repellents which include components extracted from citronella, cinnamon, cedar, eucalyptus, mints, lemongrass, geranium, and soybean. Neem oil, an extract of the Neem tree, Azadirachta indica, is another natural product that has shown repellency of Anopheles mosquitoes. However, these products do not offer residual control equivalent to standards, such as DEET. Citronella, for example, is known to be weakly repellent and highly volatile. Citronella candles have been shown to be marginally effective, if at all.
Thus, what is needed is a biorepellent without toxic or environmental concerns, but which can provide effective repellency against target pests.